The present invention relates generally to medical electronic devices, and specifically to implantable electrical muscle stimulators.
Urinary stress incontinence affects millions of people, causing discomfort and embarrassment, sometimes to the point of social isolation. Stress incontinence results from weakness or inability of pelvic muscles to hold back urinary flow from the bladder when abdominal pressure increases due to everyday events such as coughing, laughing or mild physical exertion. Muscles involved in controlling the urinary flow include primarily the urethral sphincter and the levator ani, with the cooperation of fibromuscular extensions along the urethra and other muscles in the general region of the pelvic diaphragm. In the United States, it is estimated that 10-13 million patients seek medical care for incontinence each year, of whom about 35% suffer from stress-type incontinence.
Stress incontinence is typically associated with either or both of the following anatomical conditions:
Urethral hypermobilityxe2x80x94Weakness of or injury to pelvic floor muscles causes the bladder to descend during abdominal straining or pressure, allowing urine to leak out of the bladder. This is the more common source of stress incontinence.
Intrinsic sphincter deficiencyxe2x80x94In this condition, the urethral musculature is unable to completely close the urethra or keep it closed during stress.
A large variety of products and treatment methods are available for personal and medical care of incontinence. Most patients suffering from mild to moderate incontinence use diapers or disposable absorbent pads. These products are not sufficiently absorbent to be effective in severe cases. They are uncomfortable to wear, and cause skin irritation, as well as unpleasant odors. Other non-surgical products for controlling incontinence include urethral inserts (or plugs) and externally-worn adhesive patches. Drugs are also used in some cases.
Various surgical procedures have been developed for bladder neck suspension, primarily to control urethral hypermobility by elevating the bladder neck and urethra. These procedures typically use bone anchors and sutures or slings to support the bladder neck. The success rates for bladder neck suspension surgery in controlling urinary leakage are typically in the 60-80% range, depending on the patient""s condition, the surgeon and the procedure that is used. The disadvantages of surgery are its high cost, need for hospitalization and long recovery period, and high frequency of complications.
For serious cases of intrinsic sphincter deficiency, artificial urinary sphincters have been developed. For example, the AMS 800 urinary sphincter, produced by American Medical Systems Inc., of Minnetonka, Minn., includes a periurethral inflatable cuff, used to overcome urinary incontinence when the function of the natural sphincter is impaired. The cuff is coupled to a manually-operated pump and a pressure regulator chamber, which are implanted in a patient""s body together with the cuff. The cuff is maintained at a constant pressure of 60-80 cm of water, which is generally higher than the bladder pressure. To urinate, the patient releases the pressure in the cuff by pressing on the implanted pump, which pumps the fluid out of the cuff to the chamber. Aspects of this system are described in U.S. Pat. No. 4,222,377, whose disclosure is incorporated herein by reference.
This artificial sphincter has several shortcomings, however. The constant concentric pressure that the periurethral cuff exerts on the urethra results in impaired blood supply to tissue in the area, leading to tissue atrophy, urethral erosion and infection. Furthermore, the constant pressure in the cuff is not always sufficient to overcome transient increases in bladder pressure that may result from straining, coughing, laughing or contraction of the detrusor muscle, for example. In such cases, urine leakage may result.
U.S. Pat. Nos. 4,571,749 and 4,731,083, whose disclosures are incorporated herein by reference, describe an artificial sphincter device whose pressure can vary in response to changes in abdominal or intravesical (bladder) pressure. The device includes a periurethral cuff with subdermal pump and pressure regulator, with the addition of a hydraulic pressure sensor. This system is complicated, however, and requires manual manipulation of the subdermal pump and cuff control.
Medtronic Neurological, of Columbia Heights, Minn., produces a device known as Interstim for treatment of urge incontinence, which is a different disorder from stress incontinence. In urge incontinence, a sudden, urgent need to pass urine causes involuntary urination, before the patient can get to a toilet, The condition may be caused by damage to nerve pathways from the brain to the bladder or by psychosomatic factors, leading to involuntary bladder contraction. Interstim uses an implantable pulse generator, which is surgically implanted in the lower abdomen and wired to nerves near the sacrum (the bone at the base of the spine) in a major surgical procedure under general anesthesia. Electrical impulses are then transmitted continuously to a sacral nerve that controls urinary voiding. The continuous electrical stimulation of the nerve has been found to reduce or eliminate urge incontinence in some patients.
Exercise and behavioral training are also effective in some cases in rehabilitating pelvic muscles and thus reducing or resolving incontinence. Patients are taught to perform Kegel exercises to strengthen their pelvic muscles, which may be combined with electrical stimulation of the pelvic floor. Electromyographic biofeedback may also be provided to give the patients an indication as to the effectiveness of their muscular exertions. Retraining muscles is not possible or fully effective for most patients, however, particularly when there may be neurological damage or other pathologies involved.
U.S. Pat. No. 3,626,538, whose disclosure is incorporated herein by reference, describes apparatus for stimulating a muscle, using an electromyogram (EMG) signal sensed in the muscle. If the signal is greater than a predetermined threshold value, a stimulator circuit applies a voltage to electrodes adjacent to the muscle. The apparatus is said to be particularly useful in overcoming incontinence.
Various types of electrodes have been proposed for applying electrical stimulation to pelvic muscles so as to prevent unwanted urine flow through the urethra. For example, U.S. Pat. No. 5,562,717 describes electrodes that are placed on the body surface, typically in the areas of the porineum and the sacrum, and are electrically actuated to control incontinence. U.S. Pat. No. 4,785,828 describes a vaginal plug having electrodes on an outer surface thereof. A pulse generator in the plug applies electrical pulses to the electrodes so as to constrict the pelvic muscles and prevent urine flow. U.S. Pat. No. 4,153,059 describes an intra-anal electrode, to which repetitive electrical pulses are applied in order to control urinary incontinence. U.S. Pat. No. 4,106,511 similarly describes an electrical stimulator in the form of a plug for insertion into the vagina or the anus. U.S. Pat. No. 3,866,613 describes a pessary ring having two electrodes thereon, which are energized to control incontinence. The disclosures of all of the above-mentioned patents are incorporated herein by reference.
U.S. Pat. No. 4,580,578, whose disclosure is also incorporated herein by reference, describes a device for stimulating the sphincter muscles controlling the bladder. A supporting body is fitted into the patient""s vulva between the labia, so that two electrodes attached to the supporting body contact the epidermal surface on either side of the external urethral orifice. Electrical impulses are applied to the electrodes to stimulate the region of the sphincter.
It is an object of some aspects of the present invention to provide an improved device and method of treatment for incontinence, particularly urinary stress incontinence.
It is a further object of some aspects of the present invention to provide a device and method for enhancing function of muscles, particularly those associated with urine control.
In preferred embodiments of the present invention, an implantable device for treatment of urinary stress incontinence comprises a control unit and one or more electrodes coupled to the control unit. The electrode or electrodes are preferably implanted in the genital region of a patient so as to contact one or more of the muscles that are used in regulating urine flow from the bladder. The control unit is preferably implanted under the skin of the abdomen or genital region. Motion of or pressure on or in the area of the bladder generates an electromyographic (EMG) signal in the muscles, which is sensed by the one or more electrodes and analyzed by the control unit. Alternatively or additionally, non-electromyographic signals are received and analyzed by the control unit, as described hereinbelow. When the control unit determines that the signals are indicative of a condition, such as an increase in abdominal or intravesical pressure, that is likely to cause involuntary urine flow from the bladder, it applies an electrical waveform to the electrode or electrodes, stimulating the contacted muscle to contract and thus to inhibit the urine flow.
In some preferred embodiments of the present invention, the device also includes one or more other physiological sensors, which generate signals responsive to motion or to intravesical or abdominal pressure, or to urine volume in the bladder. These signals are thus indicative of possible incontinence that may occur due to coughing, laughing, or other strain or motion of the abdominal muscles. On the other hand, when the urine volume in the bladder is low, there will be no urine flow even when the abdominal pressure does increase. The control unit processes the signals from the other sensors and uses them to determine when the electrical stimulation should be applied to the muscles.
Preferably, the control unit comprises a processor, which is programmed to distinguish between signals indicative of possible incontinence and other signals that do not warrant stimulation of the muscles. In particular, the processor is preferably programmed to recognize signal patterns indicative of normal voiding, and does not stimulate the muscles when such patterns occur, so that the patient can pass urine normally. Preferably, the processor analyzes both long-term and short-term variations in the signals, as well as rates and patterns of change in the signals. Most preferably, in response to the analysis, the processor: (a) makes an assessment of the patient""s physiological condition, such as of the patient""s bladder fill level, (b) responsive to the assessment, adjusts a time-varying threshold level associated with an aspect of the EMG signal (e.g., magnitude and/or rate) that varies over time, and (c) applies the stimulation only when a transient variation in the aspect of the EMG signal exceeds the threshold.
Further preferably, in order to reduce consumption of electrical power, the control unit comprises a low-power, low-speed processor, which monitors the EMG signals continuously, and a high-speed processor, which turns on only when the low-speed processor detects an increase in EMG activity. The high-speed processor performs an accurate analysis of the signals to determine whether stimulation is actually warranted. The inventors have found that the signals must generally be analyzed at a sample rate greater than 1000 Hz in order to accurately forecast whether or not involuntary urine loss is about to occur.
Preferably, the electrodes are implanted (unlike electrical muscle stimulators known in the art) and generally apply electrical stimulation directly into the muscle only when contraction is actually required, preferably as indicated by intrinsic physiological signals. At other times, stimulation is not applied, and the muscles are allowed to relax. Implantation of the device provides reliable, typically long-term control of muscle function, and relieves incontinence in a manner that is unobtrusive and minimizes inconvenience and discomfort of the patient. The stimulation mimics the natural function of the muscles in maintaining urinary continence. Repeated stimulation using these embodiments of the present invention also tends to exercise and strengthen the muscles, thus enhancing their inherent capability to control urine flow. Direct stimulation of the muscles, in accordance with the principles of these embodiments of the present invention, is believed to be effective against urine loss due to substantially all common types of stress incontinence.
Although preferred embodiments of the present invention are described with reference to treatment of urinary stress incontinence, it will be appreciated that the principles of the present invention may be applied as well to treat other types of urinary incontinence, such as urge incontinence, to fecal incontinence, and to treat and enhance the function of other muscles in the body. Alternatively or additionally, principles of the present invention may be applied to treating constipation or pathological retention of urine, typically by stimulating some muscles to contract (e.g., muscles of the colon), while stimulating some parasympathetic nerves to induce relaxation of other muscles (e.g., the muscles of the anus). These applications of the invention may be particularly useful following spinal cord injury.
There is therefore provided, in accordance with a preferred embodiment of the present invention, a device for treatment of urinary stress incontinence, including:
at least one electrode, which is implanted in a pelvic muscle of a patient; and
a control unit, which receives signals indicative of abdominal stress in the patient and responsive thereto applies an electrical waveform to the electrode which stimulates the muscle to contract, so as to inhibit involuntary urine flow through the patient""s urethra due to the stress.
Preferably, the signals include electromyographic signals received from the at least one electrode, and the device includes a switch between the electrode and an input of the control unit, which switch is opened when the electrical waveform is applied so as to prevent feedback from the electrode to the input.
Preferably, the control unit includes a processor, which analyzes the signals so as to determine when an involuntary urine flow is likely, whereupon the waveform is applied. Further preferably, the processor distinguishes between signals indicative of an involuntary urine flow and signals indicative of voluntary voiding by the patient. Preferably, the processor is programmable to vary one or more parameters associated with the application of the waveform, and the device includes a wireless receiver, which receives data for programming the processor from a programming unit outside the patient""s body.
Preferably, the processor""s analysis is performed on substantially non-rectified data. Further preferably, the processor analyzes the signals using spectral analysis. Most preferably, the spectral analysis is performed by the processor on substantially non-rectified data.
Preferably, the at least one electrode includes a single unipolar electrode or, alternatively or additionally, a pair of bipolar electrodes. Further preferably, the at least one electrode includes a flexible intra-muscular electrode.
In a preferred embodiment, the device includes a physiological sensor coupled to the patient""s bladder, which sensor provides at least some of the signals to the control unit. Preferably, the sensor includes a pressure sensor or, alternatively or additionally, an acceleration sensor.
Preferably, the at least one electrode and the control unit are implanted in the body of the patient, and the control unit includes a rechargeable power source. Most preferably, the power source is recharged by inductive energy transfer, substantially without electrical contact between the control unit and any object outside the patient""s body.
Preferably, the pelvic muscle includes the levator ani muscle or, alternatively or additionally, the urethral sphincter muscle or another muscle adjacent to the urethral sphincter muscle.
There is further provided, in accordance with a preferred embodiment of the present invention, a device for treatment of urinary incontinence in a patient, including:
a sensor, which is coupled to generate a signal responsive to a fill level of the patient""s bladder; and
a control unit, which receives and analyzes the signal from the sensor so as to determine a fill level of the bladder and responsive thereto applies stimulation to a pelvic muscle of the patient, so as to inhibit involuntary flow of urine through the patient""s urethra when the fill level of the bladder is above a threshold level.
Preferably, the control unit receives a further signal indicative of abdominal stress and applies the stimulation to the pelvic muscle responsive to the stress except when the fill level of the bladder is below the threshold level. In a preferred embodiment, the sensor includes an electrode, which is placed in electrical contact with the pelvic muscle of the patient to receive an electromyogram signal therefrom indicative of the stress and of the fill level.
Preferably, the device includes an electrode, which is placed in electrical contact with the pelvic muscle of the patient, and the control unit applies an electrical waveform to the electrode so as to stimulates the muscle to contract, thereby inhibiting the involuntary flow of urine.
In another preferred embodiment, the sensor includes a pressure sensor or, alternatively or additionally, an ultrasound transducer.
There is moreover provided, in accordance with a preferred embodiment of the present invention, a device for treatment of urinary stress incontinence, including:
at least one electrode, which is placed in electrical contact with a pelvic muscle of a patient; and
a control unit, which receives electromyogram signals from the electrode indicative of abdominal stress in the patient, and which determines a threshold signal level that varies over time responsive to a condition of the patient, and which, responsive to a transient increase in the electromyogram signal above the threshold level, applies an electrical waveform to the electrode which stimulates the muscle to contract, so as to inhibit involuntary urine flow through the patient""s urethra due to the stress.
Preferably, the threshold signal level varies over time responsive to temporal variation of a mean value of the electromyogram signals. Additionally or alternatively, the threshold signal level increases responsive to time elapsed since the patient last passed urine or responsive to an increase in a fill level of the patient""s bladder.
There is additionally provided, in accordance with a preferred embodiment of the present invention, a device for treatment of urinary stress incontinence, including:
at least one electrode, which is placed in electrical contact with a pelvic muscle of a patient; and
a control unit, which receives electromyogram signals from the electrode and, responsive to a rate of change of the signals indicative of a possible involuntary urine flow, applies an electrical waveform to the electrode which stimulates the muscle to contract, so as to inhibit the involuntary urine flow.
Preferably, when the rate of change is below a threshold rate, the control unit withholds the waveform so as to allow voluntary voiding.
There is also provided, in accordance with a preferred embodiment of the present invention, a method for treatment of urinary stress incontinence of a patient, including:
implanting an electrode in a pelvic muscle of the patient;
receiving a signal from the patient""s body indicative of abdominal stress; and
responsive to the signal, applying an electrical waveform to the electrode, which stimulates the muscle to contract so as to inhibit involuntary urine flow through the urethra due to the stress.
Preferably, applying the electrical waveform includes implanting an electrode in the patient""s body in electrical contact with the pelvic muscle, most preferably with the levator ani muscle or, alternatively or additionally, in contact with the urethral sphincter muscle or in proximity thereto.
Further preferably, applying the waveform includes applying a waveform to the electrode in a unipolar mode. Alternatively or additionally, implanting the electrode includes placing at least two electrodes in electrical contact with the muscle, and applying the waveform includes applying a waveform between the electrodes in a bipolar mode.
Preferably, receiving the signal includes receiving an electromyographic signal.
In a preferred embodiment, receiving the signal includes receiving a signal indicative of pressure on the patient""s bladder or, alternatively or additionally, receiving a signal indicative of motion of the patient""s bladder.
Preferably, applying the waveform includes analyzing the signal to determine when an involuntary urine flow is likely, and applying a waveform dependent on the determination, wherein analyzing the signal preferably includes distinguishing between a signal indicating that the involuntary urine flow is likely and another signal indicative of voluntary voiding.
Preferably, analyzing the signal includes analyzing substantially non-rectified data. Further preferably, analyzing the signal includes performing a spectral analysis. Most preferably, performing the spectral analysis includes performing the spectral analysis on substantially non-rectified data.
In a preferred embodiment, applying the waveform includes varying a parameter of the waveform selected from a group including amplitude, frequency, duration, wave shape and duty cycle. Alternatively or additionally, applying the waveform includes applying a pulse burst.
There is further provided, in accordance with a preferred embodiment of the present invention, a device for treatment of urinary stress incontinence, including:
at least one electrode, which is placed in electrical contact with a pelvic muscle of a patient; and
a control unit, which receives signals indicative of impending, urine flow, and distinguishes signals indicative of an involuntary urine flow from signals indicative of voluntary voiding by the patient, and responsive thereto applies an electrical waveform to the electrode which stimulates the muscle to contract, so as to inhibit involuntary urine flow.
Preferably, the control unit distinguishes between the signals indicative of an involuntary urine flow and the signals indicative of voluntary voiding, substantially without application of an input to the control unit from outside the patient""s body.
There is still further provided, in accordance with a preferred embodiment of the present invention, a device for treatment of urinary stress incontinence, including:
at least one electrode, which is placed in electrical contact with a pelvic muscle of a patient; and
a control unit, which receives at a sample rate substantially greater than 1000 Hz signals indicative of abdominal stress in the patient, analyzes the signals so as to determine when an involuntary urine flow is likely and responsive thereto applies an electrical waveform to the electrode which stimulates the muscle to contract, so as to inhibit involuntary urine flow through the patient""s urethra due to the stress.
There is moreover provided, in accordance with a preferred embodiment of the present invention, a device for treatment of urinary stress incontinence, including:
at least one electrode, which is placed in electrical contact with a pelvic muscle of a patient;
a first processor, which receives signals indicative of abdominal stress in the patient and analyzes the signals substantially continuously at a low data analysis rate; and
a second processor, which, responsive to a determination by the first processor that involuntary urine flow is likely to occur, is actuated by the first processor to analyze the signals at a high data analysis rate and, responsive to the analysis at the high data rate, applies an electrical waveform to the electrode which stimulates the muscle to contract, so as to inhibit involuntary urine flow.
There is also provided, in accordance with a preferred embodiment of the present invention, a method for treatment of urinary stress incontinence of a patient, including:
placing an electrode in electrical contact with a pelvic muscle of the patient;
receiving a signal from the patient""s body indicative of abdominal stress;
analyzing the received signal to distinguish between a signal indicating that involuntary urine flow is likely and another signal indicative of voluntary voiding; and
responsive to the analysis, applying an electrical waveform to the electrode, which stimulates the muscle to contract so as to inhibit involuntary urine flow.
There is further provided, in accordance with a preferred embodiment of the present invention, a method for treatment of urinary stress incontinence of a patient, including:
placing an electrode in electrical contact with a pelvic muscle of the patient;
receiving at a sample rate substantially greater than 1000 Hz signals indicative of abdominal stress;
analyzing the signals so as to determine when an involuntary urine flow is likely; and
responsive to the analysis, applying an electrical waveform to the electrode, which stimulates the muscle to contract so as to inhibit involuntary urine flow.
The present invention will be more fully understood from the following detailed description of the preferred embodiments thereof, taken together with the drawings in which: